Travelling drives of this kind are known from practice and are described, for example, in special print no. 1/79 (fluid February 1979), published by Hydromatik GmbH, for a wheel loader. The hydrostatic driving gear of this known travelling drive, for the purpose of changing its transmission ratio, is primary-adjustable in a first travel range, i.e. by changing the stroke volume of the hydraulic pump, and secondary-adjustable in a second travel range, i.e. by changing the stroke volume of the hydraulic motor, and consequently has a large conversion range, which allows the application of large tractive forces on the one hand and the attainment of high travelling speeds on the other hand. Both the primary and the secondary adjustment take place in dependence upon a control pressure proportional to the speed of the drive motor and changing with its load. In addition, a pressure regulation is provided, which adjusts the hydraulic motor in dependence upon the operating pressure in the operating line, likewise changing with the load, in such a way that it generates the respectively required torque necessary to overcome the respective travel resistance.
This known travelling drive has proven itself in practice; although in certain travel situations it leads to superfluous and disturbing irregularities of the travelling speed. These are, for example, travel situations with changes of the driving-gear load, for example due to load fluctuations of an operating or work drive connected to the travelling drive or fluctuations of the travel resistance, which occur for such a short period, for example upon the crossing of so-called corrugated-sheet tracks or potholes with the consequence of pressure peaks in the operating line or slipping of drive wheels, that, due to the speed-dependent control and pressure regulation used, they lead to an undesirably rapid response and adjustment of the hydrostatic driving gear.